Alcoholism is a common heterogenous disease. Heritability has been established in both men and women, but as for other psychiatric diseases, it has proved difficult to map genes directly for reasons such as genetic heterogeneity, phenocopies, penetrance and expressivity, and polygenic effects. We have identified a trait-specific marker for alcoholism vulnerability, the low voltage alpha (LVA) EEG, a normal variant of the resting EEG in which the alpha rhythm is virtually absent. This phenotype is strongly heritable, traitlike, present in 4-11% of the population and accurately determined. We now have a complete data set, including EEG and ERP phenotypes, blind- rated DSM-III-R diagnoses, psychometric tests and DNA on 247 individuals. We have recently replicated the association of LVA with a subtype of alcoholism with anxiety (Enoch et al 1995) in a comparable sample of 149 unrelated individuals. LVA was found in 23% of alcoholics, 25% of subjects with an anxiety disorder and 56% alcoholics with an anxiety disorder as compared to 8% of the individuals without alcoholism or an anxiety disorder. In order to obtain sufficient power to map genes for alcoholism, the focus of this study has shifted to a Plains American Indian tribe which has a high prevalence of alcoholism. Thus far we have an extensive data set (psychiatric diagnoses and DNA) on 350 tribal members from large pedigrees; an EEG pilot study conducted on 69 of these individuals showed a high prevalence of the LVA phenotype. Formerly titled "Genetics studies of the electroencephalogram and event-related potentials."